This invention is directed to the providing of corrugated pipe, and more particularly to the providing of corrugated pipe of the type used in the drainage of soil for agricultural, residential, recreational, or civil engineering construction purposes, including but not limited to storm sewer uses. In this particular market, clay or concrete tile, tube, or pipe was traditionally utilized. In practice, the drainage pipe was installed through the placing together of relatively short sections of the pipe to construct the desired drainage system. Such sections or pieces could range from a few feet to more than a couple of dozen feet. Consequently, construction was extremely time consuming and relatively expensive because of the number of pieces and total weight associated with the components of the drainage system. Additionally, the relatively large number of pipes which were required to be installed for such systems necessitated proper positioning of an extremely large numbers of pipe in order to insure minimal leakage.
More recently, plastic began to be used as a construction material for drainage pipe. Originally, sections of the plastic pipe or tubing were provided in predetermined lengths or sections which then were interconnected by using separate couplers or coupling units. Sometimes pipe or tubing of a relatively small diameter rolls of more than 200 feet can be used, which can impact on cost savings and ease of assembly. For pipe with greater diameters, ease of assembly and cost savings often focused on the manufacture of the coupler and the ease of installation.
This focusing on coupler structure resulted in numerous couplers for use with corrugated pipe, all of which had an exterior diameter greater than the exterior diameter of the sections of installed pipe. Consequently, it became necessary to dig a trench wide enough to accommodate the diameter of the installed coupler and to also dig a hole in the pipe bedding to accomodate this coupler and maintain proper line and grade. Additional ground needed to be disturbed and additional fill needed to be replaced, both of which factors would drive up the cost of installation.
As mentioned briefly above, couplers are well known in the prior art. A typical type of coupler could involve a polyethylene wrap secured about the adjacent ends of pipe by a fastener. These split-couplers normally require an overlap, such that the gap between the interior surface of the coupler and the exterior surface of the pipe is invariably present. Even if a gasket is placed between the adjacent pieces of pipe, installation in conjunction with the wrapped coupler may still result in a leak. A coupler similar to this is disclosed in U.S. Pat. No. 3,239,254 to Campbell.
Another type of coupler involves a heat shrink wrap as is disclosed in Lupke, et al, U.S. Pat. No. 4,141,576. Obviously, this type of coupler has disadvantages and applications with large diameter corrugated pipe where there is a need for the pipe to remain water-tight over an extended period of time.
A number of couplers are known which comprise two arcuate sections, hinged or independent of one another, with these two sections being secured together. Examples of such couplers include Borsch, et al, U.S. Pat. No. 4,443,031, and Pate, U.S. Pat. No. 4,647,074. However, both of these couplers are specifically designed to work with annular conduit systems, as opposed to helical. This distinction is important, because it is far easier to effect a water-tight seal on an annular system than it is with helical due to the configuration of the respective conduit structures. Meanwhile, many types of extruded pipe are formed using the helical technique.
Several patents disclose couplers for use with helical pipe. Examples of such patents include Hall, U.S. Pat. No. 4,149,740 and Kaminski, U.S. Pat. No. 4,795,197. Hall discloses a pipe coupler for use with pipe which appears substantially helical. However, interestingly enough the ends of each pipe section with which the coupler of Hall can be used either must be flat and level as shown in FIG. 3 of Hall, or fabricated with the outwardly extending flanges as shown in its FIG. 2. Consequently, Hall recognized the problem associated with trying to obtain a water tight seal in true helical pipe.
The Kaminski patent discloses a coupling for seed and fertilizer hoses, and as such is not concerned with whether the coupling is effectively water-tight. Its concern is providing a relatively air-tight seal. Although the coupling of Kaminski could be used with true helical pipe, it would not be expected to perform in drainage applications so as to guarantee the integrity of the drainage system.
Ideally it would be desirable to lay corrugated drainage pipe that would incorporate an in-line bell. A plastic pipe having an in-line bell is shown in Hegler, U.S. Pat. No. 5,071,173, however, this pipe is specifically designed for sewer pipe reconstruction, a practice known in the trade as relining. The pipe of Hegler was not designed to serve as the initial drainage pipe laid at a particular location.
Shroy, et al, U.S. Pat. No. 3,926,222, discloses a corrugated tubing with integral coupling means thereon. However, this particular invention relates only to single wall pipe, as opposed to dual wall. Additionally, no provision is made for attempting to obtain a tight seal, such as through the use of a sealing element.
An in-line bell pipe designed to serve as initial drainage pipe is shown in Goddard, U.S. Pat. No. 6,126,209. However, when subjected to internal pressure, the pipe as disclosed would not remain water-tight, a characteristic desirable in some drainage applications.
It is thus apparent that the need exists for an improved pipe which provides for a water-tight in-line bell, and especially one which is a dual-wall pipe.